zung2l (l) - Linux Manuals

zung2l: generates an m by n complex matrix Q with orthonormal columns,

NAME

ZUNG2L - generates an m by n complex matrix Q with orthonormal columns,

SYNOPSIS

SUBROUTINE ZUNG2L(

M, N, K, A, LDA, TAU, WORK, INFO )

    

INTEGER INFO, K, LDA, M, N

    

COMPLEX*16 A( LDA, * ), TAU( * ), WORK( * )

PURPOSE

ZUNG2L generates an m by n complex matrix Q with orthonormal columns, which is defined as the last n columns of a product of k elementary reflectors of order m

Q  =  H(k) . . . H(2) H(1)
as returned by ZGEQLF.

ARGUMENTS

M (input) INTEGER

The number of rows of the matrix Q. M >= 0.

N (input) INTEGER

The number of columns of the matrix Q. M >= N >= 0.

K (input) INTEGER

The number of elementary reflectors whose product defines the matrix Q. N >= K >= 0.

A (input/output) COMPLEX*16 array, dimension (LDA,N)

On entry, the (n-k+i)-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by ZGEQLF in the last k columns of its array argument A. On exit, the m-by-n matrix Q.

LDA (input) INTEGER

The first dimension of the array A. LDA >= max(1,M).

TAU (input) COMPLEX*16 array, dimension (K)

TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by ZGEQLF.

WORK (workspace) COMPLEX*16 array, dimension (N)

INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -i, the i-th argument has an illegal value